:) Cell Division And Cellular.Organisms Flashcards
What are the stages of the cell cycle?
Synthesis Gap phase 1 G1 checkpoint M phase Gap phase 2 G2 checkpoint Synthesis
G2 checkpoint
Cell checks whether all DNA has been replicated without any damage
If it had the cell can enter mitosis
M phase
Mitosis (nuclear division) and cytokinesis
(Cytoplasmic division) Metaphase checkpoint
Gap phase 1
Cell grows and new organelles and proteins are made
G1 checkpoint
Cell checks that the chemicals needed for replication are present and for any damage to the DNA before entering S-phase
Gap phase 2
Cell keeps growing and proteins needed for cell division are made
Synthesis
Cell replicated its DNA ready to divide by mitosis
When does the cell cycle start and end?
Starts When a cell has been produced by cell division
Ends with cell dividing to produce two identical cell
What does the cell cycle consist of?
Period of cell growth and DNA replication (interphase)
Periods of cell division (M phase)
What is interphase subdivided into?
Cell growth
Subdivided into three different separate growth stages
G1, s and G2
How is the cell cycle regulated?
By checkpoints that occur at key points during a cycle to make sure it’s okay for the process to continue
What is mitosis needed for?
The growth of multicellular organisms (like us)
Repairing damaged tissues
Method of asexual reproduction for some plants, animals and fungi
What is mitosis really?
One continuous process
Series of division phases: prophase, metaphase, anaphase and telophase
When does interphase happen?
Before mitosis in the fell cycle
When the cell grows and replicates their DNA ready for division
Describe interphase
Cell carried out normal functions and prepares to divide
Cells DNA is unraveled and replicated to double its genetic content
Organelles replicated so it has spare ones
ATP is increased (ATP provides energy needed for cell division)
Describe prophase?
Chromosomes condense getting shorter and fatter
Tiny bundled of protein (centrioles) start moving to opposite ends of cell forming network of protein fibres (spindle)
Nuclear envelope breaks down and chromosomes lie free in the cytoplasm
What is the cell cycle? The
The process that all body cells in multicellular organisms use to grow and divide
What are the chromosomes made of when mitosis begins?
Two strands joined in the middle by a centromere. The separate strands are called chromatids
Why are there two strands?
Each chromosome has already made an indentical copy of itself during interphase. When mitosis is over, chromatids, end up as one-strand chromosome in the new daughter cells
Describe metaphase
Chromosomes (each with two chromatids) line up along the middle of the cell and become attached to the spindle by their centromere.
What happens at the metaphase checkpoint
The cell checks that all the chromosomes are attached to the spindle before mitosis can continue
Anaphase describe
Centromeres divide separating each pair of sister chromatids. The spindle contracts, pulling chromatids to opposite ends of the cell, centromere first.
Telophase
Chromatids reach opposite poles in the spindle. They uncoil and become long and thin again. Called chromosomes again. Nuclear envelope forms around each group of chromosomes so there are two nuclei
Cytokinesis
Cytoplasm divides in animal cells a cleavage furrow forms to divide the cell membrane. There are now two daughter cells that are genetically identical to the original cell to each other. Cytokinesis usually begins in anaphase and ends in telophase.
Separate process to mitosis
How can you observe the cell cycle?
Stain chromosomes
So you can see under microscope meaning you can watch what happens during mitosis.
How do you recognise cells in interphase?
The chromosomes will be spread out and not condensed
Meiosis produces what?
Gametes for sexual reproduction
What happens in sexual reproduction?
Two gametes join together at fertilisation to form a zygote. Zygote then divides and develops into a new organisms
What type of cell division is meiosis?
One that happens in the reproductive organs to produce gametes
What does meiosis involve?
A reduction division
Cells that divide by mitosis produce full number of chromosomes to start with but cells that are found that are formed from meiosis have half the number.
Cells with half the normal number of chromosomes (haploid cells)
What are cells formed by meiosis?
Genetically different because each new cell ends up with a different combination of chromosomes
Why is meiosis so important?
Without meiosis, the number of chromosomes double when the gametes fused.
What does mitosis involve in terms of divisions?
Meiosis 1 and meiosis 2
What is meiosis 1?
A reduction division
What are meiosis I and meiosis II split up into?
Prophase
Metaphase
Anaphase
Telophase
What does meiosis begin with?
Interphase
During interphase, DNA unraveled and replicates to produce double-armed chromosomes called sister chromatids
Prophase I
Chromosomes condense getting shorter and fatter
Chromosomes arrange themselves into homologous pairs and crossing-over occurs. Like in mitosis, centrioles start moving to opposite ends of the cell forming the spindle fibres. Nuclear envelope breaks down
Metaphase I
Homologous pairs line up across the centre of the cell and attach to the spindle fibres by their centromeres